ZFS: lost the ability to boot a BE

I lost the ability to boot the environment named 'r357746', I suspect 
this occurred after I set it to use OpenZFS in lieu of ZFS.

I would like to edit its /boot/loader.conf (revert to zfs_load="YES") 
but re: https://github.com/openzfs/zfs/issues/4553 I can not think of a 
way to mount the dataset.

Please, how can I proceed?

----

Re: ZFS: destroying snapshots without compromising boot environments

On 28/03/2020 15:36, Graham Perrin wrote:
> On 28/03/2020 15:19, Allan Jude wrote:
>
> > You can try to destroy the snapshot, if it is the basis of a clone, 
> then
> > you will get an error, that you'd need to destroy the BE first, so you
> > might decide to keep that snapshot. As long as you don't use the -R 
> flag
> > to zfs destroy dataset_at_snapshot, it will not destroy the clones.
> >
> > You can also use 'zfs promote' to make the clone into the parent, 
> making
> > the original parent into the clone. This allows you to destroy that
> > original and the snapshot while keeping the clone.
>
> Perfect, thank you. I was nervous about destruction without warning.
>
> Below, are the differences (in measurement) between beadm and bectl to 
> be expected?
>
> ----
>
> root_at_momh167-gjp4-8570p:~ # beadm list
> BE       Active Mountpoint  Space Created
> Waterfox -      -           15.9G 2020-03-10 18:24
> r357746f -      -            1.3G 2020-03-20 06:19
> r359249b NR     /           74.7G 2020-03-28 01:19
> root_at_momh167-gjp4-8570p:~ # beadm list -aDs
> BE/Dataset/Snapshot                            Active Mountpoint Space 
> Created
>
> Waterfox
>   copperbowl/ROOT/Waterfox                     -      - 137.0M 
> 2020-03-10 18:24
>     r359249b_at_2020-03-17-21:57:17               -      - 59.2G 
> 2020-03-17 21:57
>   copperbowl/ROOT/Waterfox_at_2020-03-20-06:19:45 -      - 67.0M 
> 2020-03-20 06:19
>
> r357746f
>   copperbowl/ROOT/r357746f                     -      - 1.2G 
> 2020-03-20 06:19
>     Waterfox_at_2020-03-20-06:19:45               -      - 59.2G 
> 2020-03-20 06:19
>
> r359249b
>   copperbowl/ROOT/r359249b_at_2020-03-17-21:57:17 -      - 15.7G 
> 2020-03-17 21:57
>   copperbowl/ROOT/r359249b                     NR     / 59.0G 
> 2020-03-28 01:19
> root_at_momh167-gjp4-8570p:~ # bectl list
> BE       Active Mountpoint Space Created
> Waterfox -      -          204M  2020-03-10 18:24
> r357746f -      -          1.21G 2020-03-20 06:19
> r359249b NR     /          74.7G 2020-03-28 01:19
> root_at_momh167-gjp4-8570p:~ # bectl list -aDs
> BE/Dataset/Snapshot                              Active Mountpoint 
> Space Created
>
> Waterfox
>   copperbowl/ROOT/Waterfox                       -      - 204M 
> 2020-03-10 18:24
>   Waterfox_at_2020-03-20-06:19:45                   -      - 67.0M 
> 2020-03-20 06:19
>
> r357746f
>   copperbowl/ROOT/r357746f                       -      - 1.21G 
> 2020-03-20 06:19
>
> r359249b
>   copperbowl/ROOT/r359249b                       NR     / 74.7G 
> 2020-03-28 01:19
>   r359249b_at_2020-03-17-21:57:17                   -      - 15.7G 
> 2020-03-17 21:57
> root_at_momh167-gjp4-8570p:~ # zfs list -t snapshot
> NAME                                                     USED AVAIL  
> REFER  MOUNTPOINT
> copperbowl/ROOT/Waterfox_at_2020-03-20-06:19:45            67.0M - 59.2G  -
> copperbowl/ROOT/r359249b_at_2020-03-17-21:57:17            15.7G - 59.2G  -
> copperbowl/iocage/releases/12.0-RELEASE/root_at_jbrowsers     8K - 1.24G  -
> copperbowl/poudriere/jails/head_at_clean                    328K - 1.89G  -
> root_at_momh167-gjp4-8570p:~ # zfs destroy 
> copperbowl/ROOT/r359249b_at_2020-03-17-21:57:17
> cannot destroy 'copperbowl/ROOT/r359249b_at_2020-03-17-21:57:17': 
> snapshot has dependent clones
> use '-R' to destroy the following datasets:
> copperbowl/ROOT/r357746f
> copperbowl/ROOT/Waterfox_at_2020-03-20-06:19:45
> copperbowl/ROOT/Waterfox
> root_at_momh167-gjp4-8570p:~ # date ; uname -v
> Sat Mar 28 15:30:57 GMT 2020
> FreeBSD 13.0-CURRENT #1 r359249: Tue Mar 24 00:12:27 GMT 2020 
> root_at_momh167-gjp4-8570p:/usr/obj/usr/src/amd64.amd64/sys/GENERIC-NODEBUG
> root_at_momh167-gjp4-8570p:~ #
>